Methods and Means for Creating Three-Dimensional Borehole Image Data

ABSTRACT

A method of creating three-dimensional borehole data is provided, including illuminating a borehole using collimated beams of electromagnetic radiation; rotating the collimated beams in a sweep of at least 360 degrees; detecting backscattered electromagnetic radiation returned from surfaces of associated illumination planes using electromagnetic radiation sensors; converting detected radiation into a corresponding set of volume image data; analyzing the volume image data using computational visualization processing techniques; and creating a three-dimensional image representative of the volume data. Imaging methodologies include a complete, radial conic-shaped surface while the imaging system remains stationary; a plurality of scans performed while longitudinally moving the imaging system a distance d through the borehole between image capture operations; and a plurality of scans performed while longitudinally moving the imaging system a distance d, where d is a distance less than or equal to the collimated beam thickness, so that adjacent scans partially overlap.

FIELD OF THE INVENTION

The present invention relates generally to creation and interpretationof three-dimensional borehole image data, and in a particular thoughnon-limiting embodiment to methods and means of measuring andcharacterizing structures disposed within or immediately surrounding theborehole of a water, oil or gas well. Also disclosed are means forrecreating imaged structures as three-dimensional data images using asoftware-enabled data reconstruction method comprising data detectedthrough backscattered radiation collection and processing.

BACKGROUND

Since water, oil and gas wells are generally lined with one or moremetal casing strings adhered to the formation surrounding the wellboreby hardened cement, it is advantageous to perform quality inspections ofthe materials used to construct the well in order to ensure long-termoperability of the well. Such materials include, but are not limited to,the geological formations themselves, the casings and the cements.

Such quality inspections include, but are not limited to, measuring thethickness or density to discover any texture characteristics andstructural defects such as mechanical flaws, inhomogeneities in thematerials, incomplete or missing materials, damage caused by geologicalor subsurface movement, time varying modification of the strata behindthe casings due to fluid migration, and/or corrosion of materials.

Furthermore, wells can be fractured so that they release trappedhydrocarbons into the borehole and can be produced at the surface; inthis case the reservoir rock is fractured by the operator by pumpingspecially designed fluids into the well at pressures high enough to makefissile subsurface rocks crack along fault lines. The effectiveness ofthis approach is critically dependent upon the fracture aperture and thelateral extent of the fracture. A means to geometrically characterizethe fracture system, as well as a measurement of in situ stresses in theformation, are therefore important in predicting and measuring thepropagation and extent of the fracture into the reservoir.

There are currently several non-destructive methods of well inspectionavailable to operators, viz.:

-   -   1. Mechanical means, such as in-bore multi-fingered calipers;    -   2. In-bore optical camera methods;    -   3. Near-bore ultrasonic imaging methods;    -   4. Far-bore ultrasonic imaging methods;    -   5. Sonic logging methods to determine cement bond quality;    -   6. Electromagnetic methods to evaluate corrosion and well        integrity; and    -   7. Electrical imaging methods used to determine the borehole        shape, and to create a resistivity map of the borehole wall that        can identify geological features as well as fractures in the        reservoir rock.

The mechanical means, such as the caliper, and the optical camera onlyproduce information pertaining to the physical inner surface of theinner-most casing of the well, and are therefore incapable of offeringoperators information regarding the status of materials outside of theinner surface, such as the cement bond or volume.

Near-bore ultrasonic imaging methods, such as rotating single ultrasonictransducers, rely upon a method of emitting ultrasonic pulses in thefrequency range of 100 to 800 kHz, and then receiving and measuringwaveforms that have been reflected from the inner and outer surface ofthe inner-most casing.

The rate of decay of the waveforms indicates the quality of the cementbond to the outer surface of the inner-most casing, and can detectfeatures as small as 2-3 centimeters in size. The resonant frequency ofthe casing provides information on the wall thickness of the casing.However, this ultrasonic method cannot be used to determine thestructure of materials outside of the cement-casing interface.

Far-bore ultrasonic imaging methods rely on multiple panoramicultrasonic transducers and imagers that compare received waveformsreflected from surfaces or interfaces of rapid density changes toinversion models of the wellbore structures created prior to theoperation. In order to solve the time-of-flight inversion needed toresolve the ultrasonic data into image data (which contains radialdistance data), the operator must create three-dimensional models of thewellbore apparatus prior to performing a data-collection operation.Thus, the operator effectively needs to know what an anomaly looks likeand where it is located in advance in order to obtain a satisfactoryimage of the anomaly. Moreover, since the method is based upon reflectedwaveforms obtained from density-change interfaces, it is incapable ofproducing meaningful data regarding the nature of the cement bond or anycement volume discrepancies.

When a sonic logging method is used, a wire line tool is run in theborehole to detect how well the cement is bonded to the casing andformation via a principle based on resonance. Casing that is not boundhas a higher resonant vibration than casing that is bound, which causesthe energy from the sonic signal to be transferred to the formation.While this effect serves to detect a poor cement bond for normal cement,it fails to distinguish between an acceptable bond and a poor bond whenlow acoustic impedance cements are used, for example as is usually thecase in deep water wells. In such instances, all casing appears to bepoorly bonded.

Another disadvantage of the method is that the measurement is averagedazimuthally around the borehole and therefore cannot identify theorientation of any breach in the cement bond. Finally, it should benoted that this method can detect bond anomalies only on the order of 25cm or greater along the longitudinal borehole axis, while vital breachesin the cement bond with smaller dimensions often occur.

There are two common electromagnetic methods used to evaluate theintegrity of the tubing or casing. First, an eddy current device can beused to measure the presence of pits and holes in the inner wall of acasing. In the best practice of this method, the eddy-currentmeasurement is used in conjunction with a flux-leakage measurement todetermine casing corrosion, the latter being sensitive to defects onboth the inner and outer walls. A transmitter coil produces a highfrequency, alternating current magnetic field that induces eddy currentsin the casing wall. These currents generate their own magnetic field,which induces a signal in two closely-spaced receiver coils. In smoothcasing, these signals are the same, but if the inner wall is pitted, thesignals are different.

Second, in a borehole within which a tubing or casing is installed, alow frequency electromagnetic wave propagation directly affected by thethickness of metal of the tubular in which it lies is transmitted andsensed within a borehole by a logging tool. The transmittedelectromagnetic wave travels radially through the well-fluid beforepermeating through the tubing wall to the area outside.

The wave then propagates along the length of the tubing beforere-entering the pipe, at which point it is measured by an array ofdetector antennae within the logging tool. As the wave propagatesthrough the metal wall of the tubular its velocity and amplitude arereduced, however, the wave is unaffected by well fluid or formationproperties. The transmitter-detector transit time and the amplitude ofthe electromagnetic wave are measured by the tool, and in turn are usedto derive wall thickness.

These two techniques are often combined in a single borehole tool sothat the measurements are made in the same run in the well. While thismethod provides an average wall thickness or detects anomalies on theinner and outer surfaces for the first tubing or casing in a well, itcannot make any measurements of a second casing or tubing in the samewell. Moreover, while multiple pads deployed to detect anomalies provideazimuthal information regarding the presence of pits or holes in thecasing, full circumferential coverage of the tubing or casing wallcannot be achieved.

Finally, in open boreholes assessed prior to being cased, an electricalcurrent can be injected into the reservoir rock by a logging tool andsensed by a plurality of electrodes; in this event the electrodes aretypically arranged to form an array disposed substantially perpendicularto the axis of the tool and deployed on mechanical pads pressed againstthe borehole wall. As the tool moves up the borehole wall, the sensedcurrent in each of the plurality of electrodes varies in proportion tothe local conductivity of the reservoir rock.

A current reading obtained from each sensing electrode is then displayedas an image spanning the circumference of the borehole as the tool movesvertically within the hole. Since the borehole fluid is more conductivethan the rock formation, any fluid which fills a fracture thatintersects the borehole results in a relatively higher current, with thecurrent increasing in value in proportion to the aperture of thefracture, thus evaluating the effectiveness of the fracture in enhancingthe production of hydrocarbons from the reservoir rock. In addition tothe measurement of the currents, the tool measures the dimensions of theborehole in two perpendicular directions, thereby indicating thedirection and magnitude of the elongation of the borehole and enabling aderivation of the in situ stress in the reservoir. This finalmeasurement may be combined with the fracture evaluation to model theextent of the fracture in the reservoir rock.

While the measurement is made on multiple arms and pads attached to thetool, it does not provide full circumferential coverage of the boreholewall. Moreover, the determination of the aperture relies on accuratemeasurements of the rock resistivity and the resistivity of the boreholefluid. Finally, the aperture determination fails to provide meaningfulinformation regarding how the aperture varies in magnitude as well asdirection as it extends into the formation and therefore provideslimited information about the fracture network.

In sum, there are no currently known technologies available to operatorsto permit detailed three-dimensional imaging of wellbore casings and thestructures within and surrounding the wellbore, which offer informationobtained from the inner surface or the inner-most casing, throughmultiple casings and annuli to a volume including the cement andgeological formations. There is similarly a lack of technologies thatpermit the detailed three-dimensional imaging of the near-wellenvironment just outside the borehole.

The invention comprises a method to measure the discrete structureswithin and immediately surrounding a borehole and to recreate saidstructures as a three-dimensional representation through mathematicalreconstructions of x-ray backscattered volume imaging. These methods arefurther embodied by means that may be used to practice the method foruse in a water, oil or gas well.

In conventional, non-destructive three-dimensional imaging methods basedupon x-ray technology, an operator acquires x-ray attenuation data inwedges through a sample by moving an x-ray source and electronic imagingdevice arranged on opposite sides of a sample around the outside of thesample. Mathematical processing, typically Radon transform orcomputational processing, via various algorithms, is applied to eachdata slice to create a three-dimensional reconstruction of the sample.The resulting reconstructions are typically displayed as two-dimensionalslice images, though the underlying data actually represent volumetricproperties of the sample. Various visualization techniques that betterrepresent the three-dimensional quality of the data are becoming moreprevalent.

In addition to x-ray computed tomography scans (CT), tomograms arecurrently derived using several other physical phenomena such as gammarays in single-photon emission computed tomography scans (SPECT),radio-waves in magnetic resonance imaging (MRI), electrons intransmission electron microscopy (TEM), and electron-positronannihilation in positron emission tomography (PET). However, alltomograms are derived from an outside-in perspective, wherein theradiation source and/or imaging device are located on the outside oraround the sample to be imaged.

The prior art teaches a variety of techniques that use x-rays or otherradiant energy to inspect or obtain information about the structureswithin or surrounding the borehole of a water, oil or gas well, thoughnone teach any type of inside-out volume imaging technique as describedand claimed later in this application.

For example, U.S. Pat. No. 3,564,251 to Youmans discloses the use of aradially scanning collimated x-ray beam used to produce an attenuatedsignal at a detector for the purpose of producing a spiral-formed log ofthe inside of a casing or borehole surface immediately surrounding thetool.

U.S. Pat. No. 7,675,029 to Teague et al. provides an apparatus thatpermits the measurement of x-ray backscattered photons from anyhorizontal surface inside of a borehole that refers to two-dimensionalimaging techniques.

U.S. Pat. No. 7,634,059 to Wraight discloses an apparatus that may beused to measure two-dimension l x-ray images of the inner surface insideof a borehole, but lacks the ability to look inside of the borehole in aradial direction.

U.S. Pat. No. 8,481,919 to Teague teaches a method of producinghigh-energy photon radiation in a borehole without the use ofradioactive isotopes, and further describes rotating collimatorsdisposed around a fixed source installed internally within theapparatus, but does not have rotatable solid-state detectors withcollimators. It further teaches the use of conical and radiallysymmetrical anode arrangements that permit the production of panoramicx-ray radiation.

US 2013/0009049 by Smaardyk discloses an apparatus that allowsmeasurement of backscattered x-rays from the inner layers of a borehole,but lacks the ability to reconstruct a three-dimensional representation.

U.S. Pat. No. 8,138,471 to Shedlock discloses a scanning-beam apparatusbased on an x-ray source, a rotatable x-ray beam collimator, andsolid-state radiation detectors that enable the imaging of only theinner surfaces of borehole casings and pipelines.

U.S. Pat. No. 5,326,970 to Bayless discloses a tool that measuresbackscattered x-rays from inner surfaces of a borehole casing with thex-ray source being based on a linear accelerator.

U.S. Pat. No. 7,705,294 to Teague et al. teaches an apparatus thatmeasures backscattered x-rays from the inner layers of a borehole inselected radial directions with the missing segment data being populatedthrough movement of the apparatus through the borehole. The apparatuspermits generation of data for a two-dimensional reconstruction of thewell or borehole, but does not disclose the geometry needed forilluminating an x-ray beam so as to permit discrimination of the depthfrom which the backscattered photons originated, rather it onlydiscloses the direction.

U.S. Pat. No. 5,081,611 to Hornby discloses a method of back projectionto determine acoustic physical parameters of the earth formationlongitudinally along the borehole using a single ultrasonic transducerand a number of receivers, which are typically distributed along theprimary axis of the tool.

U.S. Pat. No. 6,725,161 to Hillis et al. discloses a method of placing atransmitter in a borehole, and a receiver on the surface of the earth,or perhaps a receiver in a borehole and a transmitter on the surface ofthe earth, in order to determine structural information regarding thegeological materials between the transmitter and receiver.

U.S. Pat. No. 6,876,721 to Siddiqui discloses a method of correlatinginformation derived from a core-sample with information obtained from aborehole density log. The core-sample information is derived from a CTscan of the core-sample, whereby the x-ray source and detectors arelocated on the outside of the sample and thereby configured as anoutside-looking-in arrangement. Various types of information derivedfrom the CT scan, e.g., bulk density, is then compared to and correlatedwith the log information.

U.S. Pat. No. 4,464,569 to Flaum discloses a method of determining theelemental composition of earth formations surrounding a well boreholeusing detected neutron capture gamma radiation emanating from the earthformation following neutron irradiation of the earth formation by aneutron spectroscopy logging tool.

U.S. Pat. No. 4,433,240 to Seeman discloses a borehole logging tool thatdetects natural radiation obtained from the rock of the formation andlogs that information so that it may be represented in an intensityversus depth plot format.

U.S. Pat. No. 3,976,879 to Turcotte discloses a borehole logging toolthat detects and records backscattered radiation obtained from theformation surrounding the borehole by means of a pulsed electromagneticenergy or photon source, so that characteristic information can berepresented in an intensity versus depth plot format.

U.S. Pat. No. 4,883,956 to Manente et al. discloses an apparatus andmethod for investigation of subsurface earth formations using anapparatus adapted for movement through a borehole. Depending upon theformation characteristic or characteristics to be measured, theapparatus may also include a natural or artificial radiation source forirradiating the formations with penetrating radiation such as gammarays, x-rays or neutrons. The light produced by a scintillator inresponse to detected radiation is then used to generate a signalrepresentative of at least one characteristic of the radiation, and thissignal is recorded.

U.S. Pat. No. 6,078,867 to Plumb et al. discloses a method forgenerating a three-dimensional graphical representation of a boreholeby, for example, receiving caliper data relating to the borehole,generating a three-dimensional wire mesh model of the borehole from thecaliper data, and color mapping the three-dimensional wire mesh modelfrom the caliper data based on either borehole form, rugosity and/orlithology.

U.S. Pat. No. 3,321,627 to Tittle discloses a system having collimateddetectors and collimated gamma-ray sources used to determine the densityof a formation outside of a borehole so that it can be represented in adensity versus depth plot format.

There is, therefore, a long-felt need that remains unmet despite manyprior unsuccessful attempts to achieve a volume image derived from aninside-out perspective, wherein the radiation source and imaging deviceare both located within the sample, in a manner that overcomes thevarious shortcomings of the prior art.

SUMMARY

A method of creating three-dimensional borehole data is provided,including at least the steps of illuminating a borehole using one ormore collimated beams of electromagnetic radiation; rotating the one ormore collimated beams in a sweep of at least 360 degrees; detectingbackscattered electromagnetic radiation returned from one or moresurfaces of associated illumination planes using one or moreelectromagnetic radiation sensors; converting detected radiation into acorresponding set of volume image data; and analyzing the volume imagedata using computational visualization processing techniques; andcreating a three-dimensional image representative of the volume data.

Various imaging methodologies include at least a complete, radialconic-shaped surface while the imaging system remains stationary; aplurality of scans performed while longitudinally moving the imagingsystem a distance d through the borehole between image captureoperations; and a plurality of scans performed longitudinally whilemoving the imaging system a distance d through the borehole, where d isa distance less than or equal to the collimated beam thickness so thatportions of adjacent scans at least partially overlap.

Various systems, structures and means suitable for performing thesemethods are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 depicts a first embodiment comprising two revolving collimatedbeams of x-rays radially offset by 180 degrees radially. The resultingilluminated areas of the well materials, such as an inner casing,annulus, outer casing, cement and formation are imaged within theimaging system by detector arrays, which are collimated to ensure thatthey only receive backscattered radiation from the areas of theillumination planes. As the imaging system moves through the boreholethe imaged surfaces are represented by a double helical ribbon.

FIG. 2 depicts plural embodiments of the configuration disclosed in FIG.1, viz., embodiments comprising two revolving collimated beams ofradiation radially offset by 180 degrees that illuminate the volumearound the borehole, thereby creating imaging planes represented by adouble helical image-plane ribbon; three revolving collimated beamsoffset by 120 degrees, thereby producing a triple helical image-planeribbon; four revolving collimated beams offset by 90 degrees, therebyproducing a quadruple helical image-plane ribbon; or any number ‘n’ ofrevolving collimated beams offset by 360/n degrees that will produce ann-helical image plane ribbon.

FIG. 3 depicts an embodiment in which the volume around the borehole isilluminated by two reciprocating collimated beams of radiation radiallyoffset by 180 degrees. As the imaging system moves through the borehole,the imaged surfaces are represented by a pair of continuous, stackedoscillating half-conic ribbons, the form of which is illustrated to theright. Configurations such as three reciprocating collimated beamsoffset by 120 degrees thereby producing a triplet of continuous stackedoscillating third-conic ribbons, or any number ‘n’ of reciprocatingcollimated beams offset by 360/n degrees to produce n-continuous stackedoscillating 1/n-conic ribbons, are also within the scope of thisdisclosure.

FIG. 4 depicts an embodiment in which a quadruple helical image-planeribbon produced by the imaging device is used to illustrate how capturedvolume image data can be represented to an operator as longitudinaltwo-dimensional sectional views, measured relative to a centreline ofthe borehole out in stepped offsets to the edge of the imaged volume. Inan alternative embodiment, the volume image data is represented astransverse two-dimensional sections.

FIG. 5 depicts an embodiment comprising a volume around the boreholethat is illuminated by two revolving collimated beams of radiationradially offset by 180 degrees and tilted away from the transverse planeby an angle Φ. The resulting illuminated areas of the well materials,such as an inner casing, annulus, outer casing, cement and formation areimaged by detector arrays within the rotating radiation shieldenclosure. In the depicted embodiment the shield includes an aperture toensure that the detector arrays only receive backscattered radiationfrom the areas of the illumination planes. In a further embodiment theapertures image a region prescribed by an optimum collimation angle θ.

DETAILED DESCRIPTION OF SEVERAL EXAMPLE EMBODIMENTS

There are no previously known technologies available on the marketcapable of providing an operator with non-destructive means fordetermining the composition or status of materials and constructionslocated behind the inner casing of a borehole, nor of the regionssurrounding the borehole, with any significant detail.

The invention described and claimed herein therefore comprises a methodand means for permitting an operator to determine the current status ofmechanical flaws, inhomogeneity in the materials, incomplete or missingmaterials, damage caused by geological or subsurface movement, timevariant modification of the strata behind the casings attributable tofluid migration, and/or corrosion of materials. The objects of theinvention are achieved by creating accurate volume image data, which arethen analyzed in detail using computational visualization techniques.

In addition, when used in an open borehole the method permits theoperator to detect and geometrically characterize fractures intersectingthe open borehole, while at the same time providing a completedescription of the borehole geometry, thereby enabling a meaningfulestimate of in-situ stresses in the earth. This combination allows theoperator to fully characterize the fracture apertures, particularlytheir extent and variation thereof as they extend into the formation,thereby allowing for a more accurate determination of the improvement inthe permeability of the formation due to the fracture.

By employing the method the operator would gain access to a fullthree-dimensional reconstruction of the structures within and around theborehole. This volume data is then viewed as a longitudinaltwo-dimensional section from the centreline of the borehole outward instepped offsets of the operator's choosing, ranging out to the edge ofthe imaged volume created by the method. Similarly, the volume imagedata can be represented as transverse two-dimensional sections so thatcross-sectional views of regions of interest within the borehole may beanalysed in detail.

Further reprocessing will identify contiguous volumetric regions withinthe three-dimensional volume image data, thereby enabling the operatorto visually deconstruct, reduce or remove the visibility of certainsections of volumetric data to isolate key features within the boreholeconstruction. The operator can visually remove all volume elements fromtheir computationally rendered view of the image data so as to leaveonly the cement layer, for example, or so as to identify areas ofunder-sized or missing cement, etc.

The principle of this method and means is to use one or more beams ofionizing radiation to illuminate a region of borehole and itssurroundings in such a manner that a detector system can be arranged toeffectively record a two-dimensional image of the illuminated plane.When the imaging system is moved longitudinally through the borehole,additional planes are illuminated and imaged. Longitudinal stacking ofthe transverse two-dimensional images enables processing of the stackeddata such that three-dimensional volume data of the boreholesurroundings may be created. The resultant volume data set is thenanalysed to provide complete tomographic datasets of the boreholesurroundings, its geometrical makeup, and materials.

An example method of creating three-dimensional borehole data comprisesilluminating a borehole using one or more collimated beams ofelectromagnetic radiation; rotating the one or more collimated beams ina sweep of at least 360 degrees; detecting backscattered electromagneticradiation returned from one or more surfaces of associated illuminationplanes using one or more electromagnetic radiation sensors; convertingdetected radiation into a corresponding set of volume image data; andanalyzing the volume image data using computational visualizationprocessing techniques; and creating a three-dimensional imagerepresentative of the volume data.

With reference now to associated FIG. 1, an example embodiment isdepicted in which the volume around a borehole is illuminated by tworevolving collimated beams 100, 101 of electromagnetic radiation, whichare radially offset by 180 degrees and tilted away from the transverseplane of the borehole by an angle of between 0 and 90 degrees.

In another embodiment, the beams of radiation may be composed of x-rays,gamma-rays, neutrons or other spectrum of electromagnetic radiation. Theresulting illuminated areas of the well materials, such as an innercasing 102, annulus 103, outer casing 104, cement 105 and formation 106are imaged within the imaging system 109 using one or more radiationdetector arrays.

In a further embodiment the system includes a plurality of apertures toensure that the detectors only receive radiation from the direction ofthe illuminated material planes 107, 108. The radiation received can bethe result of any associated backscatter radiation interactions such asa Rayleigh scatter, a Compton scatter, x-ray fluorescence, elastic orinelastic neutron scattering interactions, neutron absorption within thematerial planes, etc. As the imaging system 109 moves longitudinallythrough the borehole, the simultaneous action of the pair of revolvingbeams causes the imaged regions to remain contiguous.

In a still further embodiment, contiguous, swept imaging regions arediagrammatically represented by a double helical ribbon 110. In eachsubsequent iteration in the same radial direction (as indicated by thecoordinate rose in FIG. 1), the imaged plane contains imaginginformation regarding specific material regions in the boreholesurroundings from the previous pass of the radiation beam, but from adifferent imaging angle compared to the collimation of the detectorarrays. The ability to collect image data of the same boreholesurrounding materials from different angles permits algorithmiccomputational analysis of the two-dimensional image ribbons necessary tocreate three-dimensional volume image data.

In one embodiment, iterative reconstruction techniques are used toreconstruct the three-dimensional volume image data. Due to the raypaths passing through well fluids and possibly several material layers,significant attenuation will occur along the paths and thus noisestatistics will be relatively poor. For example, iterative algorithmapproaches can be used to provide decreased sensitivity to noise and thecapability of reconstructing an optimal image in the case of incompleteor missing data or when image data is not distributed uniformly inangle. However, other methods of algorithmic reconstruction may be usedto transform the two-dimensional image ribbons into three-dimensionalvolume image data as will occur to the ordinarily skilled artisan.

In the example embodiment depicted in FIG. 2, the imaging system 200 isconfigured such that two revolving collimated beams of x-rays or otherelectromagnetic radiation are radially offset by 180 degrees andilluminate a discreet volume around the borehole, thereby creatingilluminated planes represented by a double helical image-plane ribbon201.

However, alternative configurations are within the scope of thisdisclosure, such as three revolving collimated beams offset by 120degrees, thereby producing a triple helical image-plane ribbon 202; fourrevolving collimated beams offset by 90 degrees, thereby producing aquadruple helical image-plane ribbon 203; or more generally any number‘n’ of revolving collimated beams offset by 360/n degrees, which willproduce an n-helical image plane ribbon, etc.

A further embodiment would permit a complete conical beam of radiationwhereby a conical imaging plane would be imaged by a single 360 degreecollimated aperture. In a still further embodiment of the imaging system200 beams of neutrons or gamma-rays as a replacement for x-rays willalso be effective.

In yet another embodiment, the method admits to the imaging of complete,radial conic-shaped surfaces while the imaging system is stationary.This method further comprises longitudinally moving the imaging system arelatively short distance through the borehole in between image captureoperations. The form of the resulting dataset will be that of anon-contiguous set of two-dimensional surfaces, which would be stackedin a three-dimensional space. Alternately, the dataset can be contiguousif the movement in each step is selected as less than the beamthickness, so that portions of subsequent scans partly overlapped.

In the example embodiment depicted in FIG. 3, the volume around theborehole is illuminated by two reciprocating collimated beams 300, 301of radiation radially offset by 180 degrees. As the imaging system 304moves longitudinally through the borehole, the imaged surfaces arerepresented by a pair of continuous, stacked oscillating half-conicribbons 302, the general form of which is illustrated to the right ofFIG. 3.

Other example configurations, such as three reciprocating collimatedbeams offset by 120 degrees, will produce a triplet of continuousstacked oscillating third-conic ribbons, and more generally, any number‘n’ of reciprocating collimated beams offset by 360/n degrees willproduce n-continuous stacked oscillating 1/n-conic ribbons. Thisapproach has the benefit of reducing the overall mechanical complexityof any imaging system means or apparatus to which the method would beapplied, as the imaging system would only need to be actuated in areciprocating angle of less than 180 degrees at any one time, makingelectrical connections simpler and less prone to failure.

Either during or after the collection of the image data, the collectedvolume data is reprocessed in order to enable an operator to view theborehole surroundings and geometrical construction as longitudinaltwo-dimensional sectional views measured from the centreline of theborehole out in a series of stepped offsets of the operator's choosing,ranging out to the edge of the imaged volume (see, for example, theexample embodiment depicted in FIG. 4 at elements 401, 402).

In an alternative embodiment, the volume image data is represented astransverse two-dimensional sections (see FIG. 4, element 403), so thatcross-sectional views of regions of interest within the borehole areacquired for detailed analysis. Further reprocessing of contiguousvolumetric regions detected within the three-dimensional volume imagedata will enable an operator to visually deconstruct, reduce or removethe visibility of certain sections of volumetric data in order toisolate key features within the borehole construction. The operator thenvisually removes all volume elements from the computationally renderedview of the image data, leaving only the cement layer, for example, soto be able to identify areas of under-sized or missing cement.

In the example embodiment depicted in FIG. 5, the volume around theborehole is illuminated by two revolving collimated beams 500, 501 ofx-rays emanating from an x-ray source 513. In this example, the beamsare radially offset by 180 degrees and tilted away from the transverseplane of the borehole by an angle Φ, which can comprise any anglebetween 0 and 90 degrees. The radiation beam is collimated by aplurality of high aspect holes 514 formed in the rotating radiationshield enclosure 509 with a collimation ratio of at least 2:1, wherebythe length of the collimator is closely approximate to twice that of thediameter of the collimator orifice. However, ordinarily skilled artisanswill recognize that a plurality of low aspect collimator holes can alsobe employed depending on desired operational parameters.

The resulting illuminated areas of the well materials, such as an innercasing 502, annulus 503, outer casing 504, cement 505 and formation 506are imaged by a plurality of detector arrays 507, 508 disposed withinthe rotating radiation shielded enclosure 509. The shield includes aplurality of apertures 512 so as to ensure that the detectors onlyreceive backscattered radiation from a specified area of theillumination planes 510, 511. That area is prescribed by the collimationangle θ, which determines the geometry of the imaging collimators 512.In one example embodiment, the detector array comprises a multi-stripdetector, or instead a quasi-one-dimensional array, so that it issegmented in the longitudinal direction (though not necessarilyperpendicularly). When combined with an appropriate imaging collimator,the detection system admits to a representative depth discrimination ofthe backscattered x-rays, thereby achieving a three-dimensionalreconstruction.

In a further embodiment, detector systems sensitive to discriminatingthe energy of scattered radiation are used to achieve one or more of aplurality of interpretive methods, including (though not limited to)x-ray fluorescence, so that elemental composition of the scatteringmedium is achieved. The fluorescent characteristics of specificelements, viz., bismuth or barium, etc., are then identified within theimaged volume. This technique admits to the identification and removalof data collected as a result of multiple scattering events or otherundesired portions of the energy spectrum.

In a still further embodiment, the x-ray source 513 and the detectorarrays 507, 508 are mechanically fixed within the radiation shieldedenclosure 509 such that they rotate together with the radiation shieldedenclosure 509. In this manner, the radiation shielded enclosure 509effectively rotates within the pressure housing that encompassed theentire imaging system. However, any means admitting to production of arotating or oscillating plurality of collimated beams can be employedwith equal efficacy.

The foregoing specification is provided for illustrative purposes only,and is not intended to describe all possible aspects of the presentinvention. Moreover, while the invention has been shown and described indetail with respect to several exemplary embodiments, those of skill inthe pertinent arts will appreciate that minor changes to the descriptionand various other modifications, omissions and additions may be madewithout departing from the scope thereof.

1. A method of creating three-dimensional borehole data, said methodcomprising: illuminating a borehole using a collimated beam ofelectromagnetic radiation; rotating said collimated beam in a sweep ofat least 360 degrees; detecting backscattered electromagnetic radiationreturned from a surface of an associated illumination plane using anassociated electromagnetic radiation sensor; converting detectedradiation into a corresponding set of volume image data; analyzing saidvolume image data using a computational visualization processingtechnique; and creating a three-dimensional image representative of saidvolume image data.
 2. The method of claim 1, further comprisingilluminating a borehole using two collimated beams of electromagneticradiation radially separated by approximately 180 degrees, therebycreating a three-dimensional data image in the shape of a double helix.3. The method of claim 1, further comprising illuminating a boreholeusing three collimated beams of electromagnetic radiation radiallyseparated by approximately 120 degrees, thereby creating a resultingthree-dimensional data image in the shape of a triple helix.
 4. Themethod of claim 1, further comprising illuminating a borehole using fourcollimated beams of electromagnetic radiation radially separated byapproximately 90 degrees, thereby creating a resulting three-dimensionaldata image in the shape of a quadruple helix.
 5. The method of claim 1,further comprising illuminating a borehole using n collimated beams ofelectromagnetic radiation radially separated by approximately 360/ndegrees, thereby creating a resulting three-dimensional data image of ann-shaped helix.
 6. The method of claim 1, further comprising tilting thetransverse plane of said collimated beam by more than zero degrees andless than or equal to approximately 90 degrees.
 7. The method of claim5, further comprising tilting the transverse plane of said collimatedbeam by more than zero degrees and less than or equal to approximately90 degrees.
 8. The method of claim 1, further comprising illuminating aborehole using a collimated x-ray beam.
 9. The method of claim 1,further comprising illuminating a borehole using a collimated gamma-raybeam.
 10. The method of claim 1, further comprising illuminating aborehole using a collimated neutron beam.
 11. The method of claim 1,wherein said detecting backscattered electromagnetic radiation returnedfrom a surface of an associated illumination plane further comprisesdetecting an associated backscatter radiation interaction.
 12. Themethod of claim 1, wherein said detecting backscattered electromagneticradiation returned from a surface of an associated illumination planefurther comprises detecting at least one of a Rayleigh scatter, aCompton scatter, and an x-ray fluorescence event.
 13. The method ofclaim 1, wherein said detecting backscattered electromagnetic radiationreturned from a surface of an associated illumination plane furthercomprises detecting at least one of an elastic neutron scattering, aninelastic neutron scattering, and a neutron absorption interaction. 14.The method of claim 1, wherein said analyzing said volume image datausing computational visualization processing techniques and saidcreating a three-dimensional image representative of said volume imagedata further comprises applying one or more iterative data processingreconstruction techniques to said volume image data.
 15. The method ofclaim 14, wherein said applying one or more iterative data processingreconstruction techniques further comprises applying one or iterativealgorithms.
 16. The method of claim 14, further comprising applying oneor more iterative data processing reconstruction techniques to saidvolume image data so that signal data attenuation is reduced.
 17. Themethod of claim 16, wherein said applying one or more iterative dataprocessing reconstruction techniques to said volume image data so thatsignal data attenuation is reduced further comprises reducing signalnoise data.
 18. The method of claim 1, further comprising using anelectromagnetic radiation sensor to detect the elemental composition ofan associated scattering medium.
 19. The method of claim 1, wherein saidmethod further comprises one or more of: imaging a complete, radialconic-shaped surface while the imaging system remains stationary;longitudinally moving the imaging system a distance d through theborehole between image capture operations, thereby resulting in aplurality of non-contiguous datasets of two-dimensional images that arestacked using computational visualization processing techniques, andthen creating an integrated three-dimensional image representative ofthe stacked volume image data; and longitudinally moving the imagingsystem a distance d through the borehole, where d is a distance lessthan or equal to the collimated beam thickness, so that portions ofadjacent scans at least partially overlap.
 20. A system for creatingthree-dimensional borehole data, said system comprising: means forilluminating a borehole using a collimated beam of electromagneticradiation; means for rotating said collimated beam in a sweep of atleast 360 degrees; means for detecting backscattered electromagneticradiation returned from a surface of an associated illumination planeusing an associated electromagnetic radiation sensor; means forconverting detected radiation into a corresponding set of volume imagedata; means for analyzing said volume image data using a computationalvisualization processing technique; and means for creating athree-dimensional image representative of said volume image data. 21.The system of claim 20, further comprising means for illuminating aborehole using two collimated beams of electromagnetic radiationradially separated by approximately 180 degrees, thereby creating athree-dimensional data image in the shape of a double helix.
 22. Thesystem of claim 20, further comprising means for illuminating a boreholeusing three collimated beams of electromagnetic radiation radiallyseparated by approximately 120 degrees, thereby creating a resultingthree-dimensional data image in the shape of a triple helix.
 23. Thesystem of claim 20, further comprising means for illuminating a boreholeusing four collimated beams of electromagnetic radiation radiallyseparated by approximately 90 degrees, thereby creating a resultingthree-dimensional data image in the shape of a quadruple helix.
 24. Thesystem of claim 20, further comprising means for illuminating a boreholeusing n collimated beams of electromagnetic radiation radially separatedby approximately 360/n degrees, thereby creating a resultingthree-dimensional data image of an n-shaped helix.
 25. The system ofclaim 20, further comprising means for tilting the transverse plane ofsaid collimated beam by more than zero degrees and less than or equal toapproximately 90 degrees.
 26. The system of claim 24, further comprisingmeans for tilting the transverse plane of said collimated beam by morethan zero degrees and more than or equal to approximately 90 degrees.27. The system of claim 20, further comprising means for illuminating aborehole using a collimated x-ray beam.
 28. The system of claim 20,further comprising means for illuminating a borehole using a collimatedgamma-ray beam.
 29. The system of claim 20, further comprising means forilluminating a borehole using a collimated neutron beam.
 30. The systemof claim 20, wherein said means for detecting backscatteredelectromagnetic radiation returned from a surface of an associatedillumination plane further comprises means for detecting an associatedbackscatter radiation interaction.
 31. The system of claim 20, whereinsaid means for detecting backscattered electromagnetic radiationreturned from a surface of an associated illumination plane furthercomprises means for detecting at least one of a Rayleigh scatter, aCompton scatter, and an x-ray fluorescence event.
 32. The system ofclaim 20, wherein said means for detecting backscattered electromagneticradiation returned from a surface of an associated illumination planefurther comprises means for detecting at least one of an elastic neutronscattering, an inelastic neutron scattering, and a neutron absorptioninteraction.
 33. The system of claim 20, wherein said means foranalyzing said volume image data using a computational visualizationprocessing technique and said means for creating a three-dimensionalimage representative of said volume image data further comprises meansfor applying one or more iterative data processing reconstructiontechniques to said volume image data.
 34. The system of claim 33,wherein said means for applying one or more iterative data processingreconstruction techniques further comprises means for applying one oriterative algorithms.
 35. The system of claim 33, further comprisingmeans for applying one or more iterative data processing reconstructiontechniques to said volume image data so that signal data attenuation isreduced.
 36. The system of claim 35, wherein said means for applying oneor more iterative data processing reconstruction techniques to saidvolume image data so that signal data attenuation is reduced furthercomprises means for reducing signal noise data.
 37. The system of claim20, further comprising means for using an electromagnetic radiationsensor to detect the elemental composition of an associated scatteringmedium.
 38. The system of claim 20, wherein said system furthercomprises one or more of: means for imaging a complete, radialconic-shaped surface while the imaging system remains stationary; meansfor longitudinally moving the imaging system a distance d through theborehole between image capture operations, thereby resulting in aplurality of non-contiguous datasets of two-dimensional images that arestacked using a computational visualization processing technique, andthen creating an integrated three-dimensional image representative ofthe stacked volume image data; and means for longitudinally moving theimaging system a distance d through the borehole, where d is a distanceless than or equal to the collimated beam thickness, so that portions ofadjacent scans at least partially overlap.